In-situ monitoring of the change in thickness of films

Abstract

The change in thickness of a film on an underlying body such as a semiconductor substrate is monitored in situ by inducing a current in the film, and as the thickness of the film changes (either increase or decrease), the changes in the current are detected. With a conductive film, eddy currents are induced in the film by a generating an alternating electromagnetic field with a sensor which includes a capacitor and an inductor.

What is claimed is: 
     
       1. A method of in-situ monitoring of the change in thickness of a conductive film on an underlying body wherein the thickness of the conductive film is decreased by removing a portion of the conductive film comprising the steps of: (a) inducing an eddy current in the film by producing a shaped alternating electromagnetic field with a sensor proximate the film; and   (b) detecting a change in the thickness of the film as it changes due to a change in the induced current.   
     
     
       2. The method of claim 1 wherein the change in the current is detected by a sensor proximate only one side of the film. 
     
     
       3. The method of claim 2 wherein the sensor comprises: an inductive means; and   a capacitor electrically connected to the inductive means.   
     
     
       4. The method of claim 2 wherein the sensor is proximate a side of the underlying body away from the film. 
     
     
       5. The method of claim 1 wherein after the portion of the conductive film has been removed, a remaining portion of the conductive film entirely covers the underlying body. 
     
     
       6. The method of claim 1 wherein after the portion of the conductive film has been removed, the underlying body is at least partially exposed. 
     
     
       7. A method of in-situ monitoring of the change in thickness of a conductive film on an underlying body comprising the steps of: (a) inducing an eddy current in the film by producing a shaped alternating electromagnetic field with a sensor proximate the film, the sensor including an inductive means and a capacitor electrically connected to the inductive means; and   (b) detecting a change in the thickness of the film as it changes due to a change in the induced current by monitoring a frequency shift associated with a resonant peak of the sensor due to the change in thickness of the conductive film.   
     
     
       8. A method of in-situ monitoring of the change in thickness of a conductive film on an underlying body comprising the steps of: (a) inducing an eddy current in the film by producing a shaped alternating electromagnetic field with a plurality of sensors located at different locations proximate the underlying body, at least one sensor including an inductive means and a capacitor electrically connected to the inductive means; and   (b) detecting a change in the thickness of the film as it changes due to a change in the induced current.   
     
     
       9. The method of claim 8 wherein the plurality of sensors are electrically connected in series. 
     
     
       10. The method of claim 8 wherein the plurality of sensors are electrically connected in parallel. 
     
     
       11. The method of claim 8 wherein each sensor is set to a unique resonant frequency. 
     
     
       12. The method of claim 11 wherein the resonant frequency of each sensor is determined by varying an inductance associated with each of the sensors. 
     
     
       13. The method of claim 11 wherein the resonant frequency of each sensor is determined by varying a capacitance associate with each of the sensors.